EPSAM

I studied B.Sc. Chemistry and Forensic Science at Keele University, graduating with first class honours in 2010. I subsequently became a postgraduate research student at Keele. I am currently in the third year of my Ph.D., studying the hydrothermal synthesis and characterisation of nuclear waste storage materials.

Bursaries and Grants:

• Keele Postgraduate Association Bursary 2013 (£500)
• EPSAM Postgraduate Researcher Development and Transferable Skills Training Fund 2012 (£200)
• Royal Society of Chemistry Conference Bursary 2011 (£150)
• Royal Society of Chemistry Solid State Chemistry Group Bursary 2013 (£250)

Affiliations:

• Associate Member of the Royal Society of Chemistry
• Member of the RSC Solid State Chemistry Group
• Student Member of the Materials Research Society

The hydrothermal synthesis and characterisation of nuclear waste storage materials

Lead Supervisor:  Dr Richard Darton

Nuclear waste production is undoubtedly a major downside to nuclear energy. Currently, much of our intermediate- and high-level waste is stored in temporary facilities with the aim of burying it in deep underground repositories by 2040 [1]. In order to achieve this, radionuclides require immobilising to prevent them from leaching into the environment. This can be achieved by incorporating the radionuclides into minerals, ceramics or glasses before encapsulation in stainless-steel canisters. In order for a material to be successful in this role it must be thermally, chemically and radioactively stable.

Figure 1: Polyhedral representation of the zircon, ZrSiO₄, structure showing a potential radionuclide doped into a zirconium site

The current plan for the disposal of high-level waste is to combine it with molten borosilicate glasses before encapsulation in stainless steel canisters. This, however, is not a perfect solution as these glasses have been found to undergo amorphisation of the newly-formed crystalline phase; over time this amorphisation can lead to microcracking and swelling thus reducing the integrity of the waste form [2]. Our research is therefore focused on ceramics as an alternative. Our research has focused on the zircon, ABO₄ (Figure 1), and pyrochlore, A₂B₂O₇ (Figure 2), structure types.

Figure 2: Pyrochlore, A₂B₂O₇, structure with one-eighth of the unit cell displayed for clarity

We use hydrothermal synthesis at low temperatures (150 – 240 ^oC) as it offers significantly greater control over the product structure and morphology than traditional solid state synthesis. Our materials show excellent thermal stability and resistance to ground water leaching and many can be synthesised in less than 72 hours.

References:

1. The Department of Energy and Climate Change and the Nuclear Decommissioning Authority,     The 2010 UK Radioactive Waste Inventory: Main Report (2011).
2. A. A. Digeos, J. A. Valdez, K. E. Sickafus, S. Atiq, R. W. Grimes and A. R. Boccaccini, J. Mater.         Sci., 38, 1597-1604 (2003).

Conference abstracts:

• M. W. French and R. J. Darton, Hydrothermal synthesis of nuclear waste storage materials, IUPAC 2013 oral presentation, Istanbul (2013).
• M. W. French and R. J. Darton, Hydrothermal synthesis of nuclear waste storage materials, RSC SSCG Christmas Meeting poster presentation, St. Andrews (2012).
• M. W. French and R. J. Darton, Hafnon as a nuclear waste storage material, MC10 poster presentation, Manchester (2011).